Obviously a very US-oriented perspective, but: yes, to the extent that the US has historically attempted at least sometimes to be a global police power, they're significantly constrained when the country they're trying to police has nuclear weapons. The US response to Russia invading Ukraine has been fundamentally different in kind from, say, Iraq invading Kuwait, in which Iraqi forces were pushed back to the border in a matter of days. There are lots of reasons for this (much greater asymmetry in conventional military forces, etc.), but at least in part this is because of US concerns that direct conflict with Russia would escalate to nuclear war. Similarly, can already start to see how US posture towards North Korea is starting to change and will likely continue to do so as a result of their nuclear advancement.

Sorry this article is about US regulators approving the use of reactors in the US, right? That’s why I wrote in a US centric way.

Why does it matter that the US has more nuclear reactors that could potentially become weapons if they already a massive arsenal of nuclear weapons?

Yeah I never quite got this. We can have Putin say “you’d better let me kill whoever I want or I’ll destroy the entire world”, but we can’t have power plants.